Magnets and Magnetic Field Exercises EN

MAGNETS AND MAGNETIC FIELD EXERCISES

Commented resolution of entrance exam exercises on

Magnets – Magnetic Field

01-(UFB) A compass has its magnetic needle oriented with one pole (M) indicating Roraima and the other (N) indicating Paraná. Next, the magnetic needle of this compass is brought very close to the end of a magnet whose poles are (P) and (Q), until stable equilibrium is reached (see figure).

  1. a) What are the magnetic poles M and N of the magnetic compass needle?
  2. b) What are the P and Q poles of the magnet?

02-(UFB) Pairs of bar magnets are arranged as shown in the following figures:

The letter N indicates the North pole and S the South pole of each of the bars. Between the magnets of each of the previous pairs (a), (b) and (c) there will be, respectively, forces of:

  1. a) attraction, repulsion, repulsion;
    b) attraction, attraction, repulsion;
    c) attraction, repulsion, attraction;
    d) repulsion, repulsion, attraction;
    e) repulsion, attraction, attraction.

03-(PUC-SP) Three bars, PQ, RS and TU, are apparently identical.

It is experimentally verified that P attracts S and repels T; Q repels U and attracts S. Therefore, it is possible to conclude that:

  1. a) PQ and TU are magnets
  2. b) PQ and RS are magnets
  3. c) RS and TU are magnets
    d) all three are magnets
  4. e) only PQ is a magnet

04-(UFB) There are three bars, AB, CD, EF, apparently identical. Experimentally it is found that:

I – end A attracts end D;

II – A attracts end C;

III – D repels end E;

Then:

  1. a) AB, CD and EF are magnets.
    b) AB is a magnet, CD and EF are iron.
    c) AB is iron, CD and EF are magnets.
    d) AB and CD are iron, EF is a magnet.
    e) CD is a magnet, AB and EF are iron.

05-(ITA) A piece of iron is placed near a magnet, as shown in the diagram below.

What is the only correct statement regarding the situation at hand?

  1. a) it is the magnet that attracts the iron
    b) it is the iron that attracts the magnet
    c) the attraction of the iron for the magnet is more intense than the attraction of the magnet for the iron
    d) the attraction of the magnet for the iron is more intense than the attraction of the iron for the magnet
    e) the attraction of the iron for the magnet is equal to the attraction of the magnet for the iron

06-(UFPA) To be attracted by a magnet, a screw needs to be:

  1. a) heavier than the magnet
  2. b) lighter than a magnet
    c) made of brass and copper
  3. d) magnetized by the proximity of the magnet
  4. e) formed by an alloy of copper and zinc

07-(UFPA ) The Earth is considered a gigantic magnet, which has the following characteristics:

  1. a) The geographic North Pole is exactly over the magnetic South Pole, and the geographic South is in the same position as the magnetic North.
  2. b) The geographic North Pole is exactly over the magnetic North Pole, and the geographic South Pole is in the same position as the magnetic South Pole.
  3. c) The magnetic North Pole is close to the geographic South Pole, and the magnetic South Pole is close to the geographic North Pole.
  4. d) The magnetic north pole is close to the geographic north pole, and the magnetic south pole is close to the geographic south pole.
  5. e) The geographic North Pole is offset by an angle of 45º from the magnetic South Pole, and the geographic South Pole is offset by 45º from the magnetic North Pole.

08-(UnB-DF) Three screwdrivers that may have magnetized tips, whose poles are X, Y and Z, are brought close to the K pole of a magnet.

We observe that the X and Y poles are attracted and Z is repelled.

If key X is a south pole, we can state that:

  1. Y is a north pole.
  2. Z and K are north pole.

III. Y is not magnetized and K is a south pole.

  1. a) only I is correct
  2. b) I and II are correct
    c) I and III are correct
  3. d) only II is correct
    e) all are correct

09-(PUC–MG) The figure shows the sunrise. Of points A, B, C and D, which one indicates the geographic South?

10-(UFRGS) The figure shows a piece of iron near one of the poles of a permanent magnet.

Select the alternative that correctly completes the gaps in the following statements about this situation.

The L end of the piece of iron is ……… by the K pole of the magnet.

Calling the south pole of the magnet S and the north pole N, a possible distribution of the poles at the K, L and M ends is, respectively, ……….

  1. a) attracted – N, N and S
  2. b) attracted – N, S and N
  3. c) repelled – N, S and N
    d) repelled – S, S and N
  4. e) repelled – S, N and S

11-(FUVEST-SP) Consider a bar magnet resting on a table. You hold another bar magnet between your fingers and investigate the magnetic forces acting on it, in the vicinity of the magnet resting on the table. You conclude that the magnet between your fingers:

  1. a) will always be attracted to the fixed magnet
  2. b) will always be repelled by the fixed magnet
    c) will always tend to rotate
    d) will neither be attracted nor repelled
  3. e) may be attracted or repelled

12-(UFB) A Physics teacher, in a magnetism experiment, sets up the scheme in the figure below, where M and N are two bars, one made of iron and the other a natural magnet, not necessarily in that order. Observing that they attract each other, he asks his students:

  1. a) Which one is the magnet?
  2. b) What would happen if the position of the two bars were reversed?

13-(UFPA) In the figure, a natural magnet, whose north, N, and south, S, magnetic poles are represented, balances two nails 1 and 2. Points A and B belong to 1 and points C and D belong to 2.

  1. a) B and C are north poles
  2. b) A is a north pole and D is a south pole
    c) A and D are both south poles
  3. d) A is a south pole and B is a north pole
    e) B is a south pole and D is a north pole

14-(UEMG-MG) Observe the following statements:

  1. On a compass, the north pole is the pole of the needle that points to the Earth’s geographic north.
  2. The pole of a magnet is the region of the magnet where the magnetism is most intense.

III. When cutting a magnet, two magnets with a single pole each are obtained.

The following are correct:

15-(UFB) The figure represents the position of a horseshoe-shaped magnet in relation to the cardinal points.

Draw the magnetic needle of a compass and its orientation when placed at point P. Assume that the magnetic forces of the Earth and the magnet on the needle have the same intensity.

16-(FUVEST) Figure I below represents a permanent bar magnet, where N and S indicate, respectively, north and south poles.

Suppose the bar is divided into three pieces, as shown in Figure II. Placing the two extreme pieces side by side, as indicated in Figure III, it is correct to state that they:

  1. a) They will attract each other, since A is the north pole and B is the south pole.
    b) They will attract each other, since A is the south pole and B is the north pole.
    c) They will neither be attracted nor repelled.
    d) They will repel each other, since A is the north pole and B is the south pole.
    e) They will repel each other, since A is the south pole and B is the north pole.

17-(UFB ) Represent, in each case, the resulting magnetic force that the north (N) and south (S) poles of magnet A exert on the north (P) and south (Q) poles of magnet B. If magnet B tends to rotate around a fixed point (G), what will be the direction of rotation in each case?

18-(UFB) Magnetization can be induced in a ferromagnetic material, such as a steel nail, by rubbing a permanent magnet on it repeatedly, always with the same pole (in this case, the north pole) and always in the same direction (in this case, to the right), as shown in the figure below.

After the nail becomes magnetized and the permanent magnet is removed, which end of the nail is the north pole and which is the south pole?

19-(UERJ-RJ) A magnetic needle passed through a cork stopper floats in a container containing water, in the position shown in figure 1, under the action of the Earth’s magnetic field.

Place another magnet around the container with its poles positioned as shown in figure 2:

The new position of the needle, under the action of the two magnetic fields, will be:

20-(UFSC-SC) The statements below refer to magnetic phenomena. Select the TRUE proposition(s).

  1. A student breaks a magnet in half, obtaining two pieces, both with a south pole and a north pole.
  2. An astronaut, upon landing on the Moon, realizes that there is no magnetic field there, so he can use a compass to orient himself.
  3. A magnetic bar will orient itself when suspended horizontally by a wire attached by its center of gravity to the ceiling of a UFSC laboratory.
  4. A non-magnetized bar will not remain fixed to the door of a demagnetized refrigerator when placed there.
  5. One way to demagnetize a compass is to place it in a hot oven.
  6. One way to magnetize a compass is to place it in a demagnetized refrigerator.

21-(PUCCAMP-SP) A small magnet attracts a nail placed at a distance x with a force   whose magnitude is inversely proportional to the square of x. 

This means that when the distance x is doubled, the value of the magnetic force   will become

  1. a) four times smaller.
  2. b) twice as small.
  3. c) the same.
    d) twice as big.
  4. e) four times larger.

22-(UNIFESP-SP) A little doll is attached, by a magnet glued to it, to the vertical door of a refrigerator.

  1. a) Draw this little figure schematically in the answer booklet, representing and naming the forces acting on it.
  2. b) If m = 20g is the total mass of the doll with the magnet and μ = 0.50 is the coefficient of static friction between the magnet and the refrigerator door, what should be the smallest value of the magnetic force between the magnet and the refrigerator so that the doll does not fall? Given: g = 10m/s2.

23-(FGV-SP) The word ‘aimant’, which translated from French means lover, gave rise to the name magnet, due to the ability of these objects to exert attraction and repulsion. Regarding these manifestations, consider the following propositions:

  1. Just as there are magnets that have both types of poles, south and north, there are magnets that have only one.
  2. the Earth’s magnetic field diverges from other fields, since the magnetic north pole of a compass is attracted to the planet’s magnetic north pole.

III. the pieces obtained from dividing a magnet are also magnets that have two magnetic poles, regardless of the size of the pieces.

The content in is correct

  1. a) I, only.
  2. b) III, only.
  3. c) I and II, only.
    d) II and III, only.
  4. e) I, II and III.

24-(PUC-PR) A piece of iron is placed near a magnet, as shown in the following figure:

Select the correct alternative:

  1. a) it is the iron that attracts the magnet.
    b) the attraction of the iron for the magnet is equal to the attraction of the magnet for the iron.
    c) it is the magnet that attracts the iron.
    d) the attraction of the magnet for the iron is more intense than the attraction of the iron for the magnet.
    e) the attraction of the iron for the magnet is more intense than the attraction of the magnet for the iron.

25-(FUVEST-SP) Four identical bar-shaped magnets, with the polarities indicated, are supported on a horizontal table, as in the figure, seen from above. A small compass is also placed on the table, at the central point P, equidistant from the magnets, indicating the direction and sense of the magnetic field of the magnets at P.

Not taking into account the effect of the Earth’s magnetic field, the figure that best
represents the orientation of the compass needle is:

26-(FGV-SP) Magnets 1, 2 and 3 were carefully sectioned into two symmetrical pieces, in the regions indicated by the dashed line.

Analyze the statements regarding the consequences of dividing the magnets:

  1. all pieces obtained from these magnets will also be magnets, regardless of the section plane used;
  2. the respective pieces of magnets 2 and 3 may spontaneously join together at the separation points, returning to the original appearance of each magnet;

III. in the section of magnets 1 and 2, the magnetic poles will be separated, keeping each fragment with a single magnetic pole.

The content is correct only in

27-(PUC-MG) A permanent magnet, in the shape of a “horseshoe”, whose north and south poles are indicated in the following figure, is divided into three parts.

It is CORRECT to conclude that:

  1. a) part 1 will have only the north pole and part 2 will have only the south pole.
  2. b) parts 1 and 2 will form new magnets, but part 3 will not.
  3. c) parts 1, 2 and 3 will lose their magnetic properties.
  4. d) parts 1, 2 and 3 will form three new magnets, each with its own north and south poles.

28-(UFPEL-RS) Consider a permanent magnet and an initially non-magnetized iron bar, as shown in the following figure.

When we bring the iron bar closer to the magnet, we observe the formation of a ______ pole in A, a ______ pole in B and a ______ between the magnet and the iron bar.

The alternative that correctly and respectively fills in the gaps in the previous statement is

  1. a) north, south, repulsion
  2. b) south, south, repulsion.
    c) south, north, attraction.
  3. d) north, south, attraction
    e) south, north, repulsion.

29-(CFT-MG) A person has two compasses, one of which is faulty and points to the geographic south of the Earth. When placed side by side, the magnetic interaction between them is much greater than between both of them and the Earth. In this case, the equilibrium orientation of both is correctly represented in:

30-(CFT-MG) A compass that orients itself in the Earth’s magnetic field, as illustrated in figure 1, is placed at point P, next to a bar-shaped magnet, shown in figure 2.

The equilibrium position of the compass at P is best represented in:

31-(UFMG-MG) A magnet and an iron block are kept fixed on a horizontal surface, as shown in the figure:

At a certain moment, both are released and move towards each other, due to the force of magnetic attraction.

Ignore any type of friction and consider that the mass “m” of the magnet is equal to half the mass of the iron block.

Let a(i) be the magnitude of the acceleration and F(i) be the magnitude of the resultant of the forces on the magnet. For the iron block, these quantities are, respectively, a(f) and F(f).

Based on this information, it is CORRECT to state that

  1. a) F(i) = F(f) and a(i) = a(f).
    b) F(i) = F(f) and a(i) = 2a(f).
    c) F(i) = 2F(f) and a(i) = 2a(f).
    d) F(i) = 2F(f) and a(i) = a(f).

32-(CFT-MG ) A bar magnet AB is split in half, and the resulting pieces are also divided into two equal parts, as shown in the following figure.

By hanging the four pieces, they are oriented in the geographic North-South direction. The poles that point in the same direction are

  1. a) E, C, G, B.
  2. b) E, F, G, H.
    c) A, F, G, B.
  3. d) A, C, D, B.

33- (UFRS-RS) Figure (a) represents a magnetized half of a razor blade, with the north and south poles indicated respectively by the letters N and S. First, this half of the blade is divided into three pieces, as indicated in figure (b). Next, pieces 1 and 3 are placed side by side, as indicated in figure (c).

Under these conditions, we can state that pieces 1 and 3 are __________, since P marks a __________ pole and Q a __________ pole.

The alternative that correctly fills in the gaps in the previous statement is:

  1. a) will attract – north – south
    b) will attract – south – north
    c) will repel – north – south
    d) will repel – south – north
    e) will attract – south – south

34-(UNIFESP-SP) With a scale and a dynamometer (an instrument for measuring forces), a student decides to investigate the action of the magnetic force of a U-shaped magnet on a small iron bar. Initially, far apart from each other, the student places the magnet on a scale and notes its mass. Then, still far from the magnet, he attaches the bar to the dynamometer and notes the force measured by it. Finally, he sets up the system in such a way that the iron bar, attached to the dynamometer, interacts magnetically with the magnet, still on the scale, as shown in the figure.

The scale now registers a smaller mass than that registered in the previous situation, and the dynamometer registers a force equivalent to

  1. a) force weight of the bar b) magnetic force between the magnet and the bar
    c) sum of the force weight of the bar with half the value of the magnetic force between the magnet and the bar
    d) sum of the force weight of the bar with the magnetic force between the magnet and the bar
    e) sum of the force weight of the bar and magnetic force between the magnet and the bar, minus the elastic force of the dynamometer spring.

35-(FATEC-SP) A child playing with a magnet, accidentally drops it, and it breaks into two pieces. When trying to fix it, joining them together at the broken point, he realizes that the two pieces do not fit together due to the magnetic action.

With this in mind, if the magnet had the shape and polarities shown in the figure below, it is valid to say that the magnet could have broken.

  1. a) in the direction of plane α
    b) in the direction of planes α and β
  2. c) in the direction of the π plane
    d) in the direction of any plane
    e) only in the direction of the β plane

36-(UFB) The figure represents the induction lines of the magnetic field of a bar magnet.

  1. a) Represent how small magnetic needles () placed at points 1, 2, 3 and 4 would be arranged.
  2. b) Represent the magnetic induction vector, , ,   and  ,

37-(UFAL-AL) Two identical bar-shaped magnets are fixed in parallel.

At the midpoint P, equidistant from the two magnets, as shown in the figure, the resulting magnetic induction vector must be represented by the vector

38-(UEL-PR) The needle of a compass assumes the position indicated in the following figure when placed in a region where there is, in addition to the Earth’s magnetic field, a uniform and horizontal magnetic field.

Considering the position of the uniform field lines, drawn in the figure, the Earth’s magnetic field vector in the region can be indicated by the vector:

39-(UEL-PR) Consider the magnetic field at points P 1 , P 2 , P 3 , P 4 „ and P 5 , in the vicinity of a bar magnet, as represented in the following figure.

The magnetic field intensity is lowest at the point:

40-(MACKENZIE-SP) The induction lines of a magnetic field are:

  1. a) the locus of points where the intensity of the magnetic field is constant
  2. b) the trajectories described by electric charges in a magnetic field
  3. c) those that at each point are tangent to the magnetic induction vector, oriented in its direction
  4. d) those that start from the north pole of a magnet and go to infinity
  5. e) none of the above is correct

41-(UFSC-SC) The figure represents the induction lines of the Earth’s magnetic field. Earth’s magnetism led to the invention of the compass, an essential instrument for the great navigations and discoveries of the 15th century and, according to historians, already used by the Chinese since the 10th century. In 1600, William Gilbert, in his work called De Magnete, explains that the orientation of the magnetic needle is due to the fact that the Earth behaves like an immense magnet, presenting two magnetic poles.

There are many phenomena related to the Earth’s magnetic field. We currently know that beams of electrified particles (electrons and protons) coming from outer space are captured by the Earth’s magnetic field when they pass near the Earth, constituting a good example of the movement of charged particles in a magnetic field.

Select the CORRECT proposition(s):

  1. The direction of the induction lines, shown in the figure, indicates that the magnetic south pole is located close to the geographic north pole.
  2. The direction of the induction lines, shown in the figure, indicates that the magnetic north pole is located close to the geographic north pole.
  3. The induction lines of the Earth’s magnetic field show that it behaves like a gigantic magnet, with two magnetic poles.
  4. The north pole of a compass needle always points to the Earth’s magnetic south pole.
  5. The magnitude of the Earth’s magnetic field increases as it moves away from the Earth’s surface.

42-(UNESP-SP) In a biophysics laboratory, a researcher carries out an experiment with “magnetic bacteria”, bacteria that have small magnets inside them.

With the help of these magnets, these bacteria are guided to reach the bottom of the lakes, where there is a greater quantity of food. Thus, due to the Earth’s magnetic field and the location of these lakes, there are regions where one type of bacteria feeds better and, therefore, can predominate over another. Suppose this researcher obtains three samples of lake water, from different regions of the Earth, containing these bacteria.

In sample A, bacteria that are oriented towards the magnetic north pole predominate, in sample B, bacteria that are oriented towards the magnetic south pole predominate and in sample C there are equal amounts of both groups.

  1. a) Using this information, copy and fill in the following table, indicating the origin of each sample in relation to the location of the lakes from which they came.
  2. b) Based on the configuration of the Earth’s magnetic field, justify the associations you made.

43-(UFMG-MG) Performing an experiment with two bar magnets, Julia placed them under a sheet of paper and spread iron filings over the sheet. She placed the magnets in two different orientations and obtained the results shown in figures I and II:

In these figures, the magnets are represented by rectangles.

Based on this information, it is CORRECT to state that the ends of the magnets facing the region between them correspond to the poles.

  1. a) north and north in figure I and south and north in figure II.
    b) north and north in figure I and south and south in figure II.
    c) north and south in figure I and south and north in figure II.
    d) north and south in figure I and south and south in figure II.

44-(UFRS-RS) A small compass is placed near a permanent magnet. At which of the positions marked in the figure will the north end of the needle point to the top of the page?

  1. a) Only A or D
  2. b) Only B or C
    c) Only A, B or D
  3. d) Only B, C or D
  4. e) In A, B, C, or D

45-(UFRJ-RJ) The field of the horseshoe magnet is explored on the surface of the cardboard, placing small compasses in positions 1, 2, 3, 4 and 5. Which of the proposed options correctly represents the orientations of the compasses?

46-(UFG-GO) Eight identical magnets are arranged on a table at the same distance from point O, taken as the origin, and oriented as shown in the figure.

Neglecting the effect of the Earth’s magnetic field, the resulting magnetic field, at O, will form an angle of

47-(UFRN-RN) In 1581, scholar Robert Norman published a book in London discussing experiments showing that the force exerted by the Earth’s magnetic field on a magnetized needle is not horizontal. This force tends to align the needle with the lines of this field. Due to this property, a compass can be built that, in addition to indicating the north-south direction, also indicates the inclination of the Earth’s magnetic field line at the location where the compass is located. This is done, for example, by inserting a magnetized needle into a material so that the whole has the same density as water and remains in equilibrium inside a glass filled with water, as shown in Figure 1.

Figure 2 represents the Earth and some of the lines of the Earth’s magnetic field. Observations were made with the aforementioned compass in three cities (I, II and III), indicating that the north pole of the needle formed, APPROXIMATELY,

– for city I, an angle of 20° in relation to the horizontal and pointing downwards;

– for city II, an angle of 75° in relation to the horizontal and pointing upwards;

– for city III, an angle of 0° and remained horizontal.

From this information, it can be concluded that such observations were carried out, RESPECTIVELY, in the cities of

  1. a) Punta Arenas (southern Chile), Natal (northeastern Brazil) and Havana (northwestern Cuba).
  2. b) Punta Arenas (southern Chile), Havana (northwest Cuba) and Natal (northeast Brazil).
  3. c) Havana (northwest of Cuba), Natal (northeast of Brazil) and Punta Arenas (south of Chile).
  4. d) Havana (northwest of Cuba), Punta Arenas (south of Chile) and Natal (northeast of Brazil).

48-(UFSCAR-SP) Two small identical magnets are shaped like parallelepipeds with a square base. Around them, each one produces a magnetic field whose lines resemble the schematic drawing.

Sufficiently far apart from each other, the magnets are cut differently. The parts obtained are separated so that there is no mutual influence and arranged, as shown in the following figure.

If the parts of magnet 1 and magnet 2 are brought together again in the region where they were cut, maintaining the original positions of each piece, it should be expected that

  1. a) the corresponding parts of each magnet attract each other, reconstituting the shape of both
  2. b) only the corresponding parts of magnet 2 join together, reconstituting the original shape of this magnet
  3. c) only the corresponding parts of magnet 1 come together, reconstituting the original shape of that magnet
  4. d) the corresponding parts of each magnet repel each other, preventing the reconstitution of both
  5. e) due to the cut, the magnetism ceases because of the separation of the magnetic poles of each of the magnets

49-(FUVEST-SP) On a flat, horizontal table, a bar-shaped magnet is placed, shown in the figure, seen from above, along with some lines of its magnetic field. A small compass is slowly moved across the table, starting from point P, making a complete circular turn around the magnet.

At the end of this movement, the compass needle will have completed, around its own axis, a number of turns equal to:
Note: Under these conditions, disregard the Earth’s magnetic field.

  1. a) 1/4 turn.
  2. b) 1/2 turn.
    c) 1 complete turn.
  3. d) 2 complete turns.
    e) 4 complete turns.

50-(FUVEST-SP) A thin, cross-shaped iron object is magnetized and has two North (N) poles and two South (S) poles. When this object is placed horizontally on a flat table, the lines that best represent, on the plane of the table, the magnetic field created by it, are those indicated in

51-(UEPG-PR)

Electromagnetism studies both electrical and magnetic interactions. Regarding electromagnetism, mark the correct statement.

01) If a magnet is broken into two parts, the south pole remains while the north pole disappears.

02) The Earth can be considered as a large magnet, whose magnetic north and south poles are located approximately at the geographic south and north poles, respectively.

04) The attraction that occurs when we bring certain minerals closer to a piece of iron is a manifestation of an electrical nature.

08) A conducting wire carrying an electric current produces deflections in a magnetized needle.

52-(FATEC-SP)

A child playing with a magnet, carelessly drops it, and it breaks into two pieces.

trying to fix it, joining them together at the point of rupture, she realizes that the two pieces do not fit together due to the magnetic action.

With this in mind, if the magnet had the shape and polarities shown in the figure below, it is valid to say that the magnet could have broken.

  1. a) in the direction of the α plane.
    b) in the direction of the β plane
  2. c) in the direction of the π plane.
    d) in the direction of any plane.
    e) only in the direction of the β plane.

53-(PUC-RJ)

Biomagnetism studies the generation and interaction of magnetic fields with living matter. One of its most recent applications is the use of magnetic particles – nanoparticles in particular – in the administration of medications. Instead of letting a medication circulate freely through the human body, with the risk of harmful side effects, the idea is to “stick” the medication to magnetic particles, inject them into the bloodstream and guide them with a magnet to the site of the disease.

Organizing these materials requires multidisciplinary skills to choose and prepare the appropriate magnetic particles;

choosing and preparing the casing and the way in which the drugs will be absorbed. Pharmacists are usually the ones who deal with the casing materials, while doctors investigate the reaction in living beings. Physicists, chemists and materials engineers are responsible for preparing the magnetic particles.

Regarding the concepts and applications of Electricity and Magnetism, it is CORRECT to state that:

  1. a) The magnetic field induction lines generated by the magnet are continuous lines that, outside the magnet, go from the north pole to the south pole.
  2. b) The medicine associated with the magnetic particle can be guided to the site of the disease through a constant electric field.
  3. c) If the guiding magnetic field were formed due to a continuous electric current, it would have a variation proportional to the square of the distance between the wire carrying the current and the magnetic particles.
  4. d) Any metallic substance can be used as a magnetic particle.
  5. e) The only way to obtain a magnetic field to guide the medication is through the use of permanent magnets.

54-(CEFET-MG)

A compass is a device consisting of a magnetized needle that can rotate freely around an axis perpendicular to it.

Regarding its operation, it is stated:

I- The magnetic south pole points to the Earth’s geographic north.

II- The magnetic north pole points south from a magnet placed near the compass.

III- The needle undergoes deflection when it is close to and parallel to a wire that conducts electric current.

IV- The needle, in the absence of external magnetic fields, is oriented in the east-west direction of the Earth.

Only the following statements are correct:

55-(UEMG-MG)

The year 2009 was the International Year of Astronomy. 400 years ago, Galileo pointed a telescope at the sky and changed the way we see the world, the universe and ourselves.

The following questions confront us with observations and remind us that we are just a part of something much bigger: the cosmos.

An astronaut, when taking a compass to the Moon, finds that the magnetic needle of the compass does not point in a preferred direction, as it does on Earth.

Consider the following statements, based on this observation:

  1. The magnetic compass needle does not create a magnetic field when it is on the Moon.
  2. The Moon does not have a magnetic field.

Regarding these statements, mark the CORRECT alternative:

  1. a) Only statement 1 is correct.
  2. b) Only statement 2 is correct.
  3. c) Both statements are correct.
    d) Both statements are false.

56-(FGV-SP)

Regarding the phenomena of magnetism, analyze:

  1. A magnet, inserted in a region where a magnetic field acts, is subject to a binary of magnetic forces of the same intensity, which are not capable of translating it, but can rotate it.
  2. When artificial magnets are produced, the position of their poles is determined by the position in which the body of the magnet is found, relative to the lines of the magnetic field to which it is subjected in its magnetization process.

III. The number of times we can divide a magnet into two parts and obtain new magnets from these parts is limited to the moment when the south and north poles are separated from the division.

  1. The Earth’s geographic and magnetic poles are not in the same place. When we use a compass, the magnetic north of its needle indicates the region where the planet’s magnetic north is located.

Only the content in is correct

  1. A) I and II.
    B) I and IV.
  2. C) II and III.
    D) I, III and IV.
  3. E) II, III and IV.

57-(UFF-RJ)

Magnets are often used to hold small objects to flat, vertical metal surfaces, such as bulletin boards and refrigerator doors.

Consider that a magnet, glued to a clip, is in contact with the door of a refrigerator. Assume that the magnetic force that the magnet exerts on the surface of the refrigerator is perpendicular to it and has magnitude F M .

. The magnet/clamp assembly has mass m o

.The coefficient of static friction between the surface of the
refrigerator and that of the magnet is μ and
.A mass M is hanging from the clamp by a string of negligible mass , as shown in the figure.

  1. a) Draw on the diagram the forces acting on the magnet/clamp assembly (represented by the black dot at the intersection of the x and y axes in the figure), identifying each of these forces.
  2. b) What is the largest value of mass M that can be hung on the clamp without the assembly falling?

58-(FUVEST-SP)

In a laboratory class, students were divided into two groups. Group A experimented with drawing lines

of electric and magnetic fields. The drawings made are presented in figures I, II, III and IV below.

The students in group B were responsible for analyzing the drawings produced by group A and formulating hypotheses. Among them, the only correct one is that figures I, II, III and IV can represent, respectively, field lines.

  1. a) electrostatic, electrostatic, magnetic and magnetic.
    b) magnetic, magnetic, electrostatic and electrostatic.
    c) electrostatic, magnetic, electrostatic and magnetic.
    d) magnetic, electrostatic, electrostatic and magnetic.
    e) electrostatic, magnetic, magnetic and magnetic.

59–(UNESP-SP)

The Earth behaves like a huge magnet, that is, it has its own magnetism. Observe the figures, which are representations of the Earth’s magnetic field.

From the observation of the figures and their knowledge, it can be stated that:

(A) If we look for the geographic coordinates of the magnetic north pole to reach the geographic pole, we probably won’t get there, because the location of
the Earth’s magnetic poles does not coincide with that of the geographic poles.

(B) the magnetic north pole is located on the north coast of Alaska and the magnetic south pole is located on the west coast of Antarctica.

(C) if we look for the geographic coordinates of the magnetic south pole to reach the geographic south pole, we will probably achieve our goal, because the location of the Earth’s magnetic poles coincides with that of the geographic poles.

(D) the magnetic north pole is located in Greenland, North America, and the geographic south pole is on the north coast of Antarctica.

(E) the magnetic north pole is located on the north coast of Canada, in the Atlantic Ocean, therefore, next to the location of the geographic north pole.

Resolutions